Support adding static pages about hexo-admin

[oeway]

+1

[nkoehring]

+1

I see pages in the menu but I need to create/delete them via console at the moment. Is the implementation planned?

[jaredly]

not actively :) I don't tend to create/delete static pages too often

[jaredly]

Useful starting points:

Server:
This is the current endpoint for getting/updating pages link. You can see below it the posts/new endpoint -- we'll need a pages/new endpoint that will just take a title, and then return the page model. Here's the call on the front-end that will use the endpoint.

Frontend:
The frontend is mostly implemented for it (see this commented out line) -- I think you'll only need to uncomment that line.

[jaredly]

Delete isn't even supported for posts yet :D but it also shouldn't be too hard. If someone wants to put together the backend endpoint, I can put a button somewhere.

[yfsoftcom]

i fix the 'new page' feature
plz accept my pr:
32dea78

[pirtleshell]

Added and merged in #120